The present invention relates to an oxy-fuel burner system for alternately or possibly simultaneously burning gaseous and liquid fuels in the presence of oxygen or oxygen enriched air. More particularly, the present invention relates to such an oxy-fuel burner system having fuel and oxidant nozzles designed to project gaseous and liquid fuel jets and one or more oxidant jets so that either gaseous or liquid fuels can be burned with combustion supported by the oxidant.
Burners are used to heat a variety of melts such as glass, ferrous and non-ferrous metals and etc. A recent burner development concerns the use of oxygen or oxygen enriched air to support combustion of a fuel in a burner known as an oxy-fuel burner. Such burners are compact and produce typically small flames with a high power output.
The disadvantage of the high power output produced by the compact flames produced by the oxy-fuel burners is that hot spots may develop in the melt because of excessive localized heat-transfer rates. In order to prevent this, burners have been developed in which combustion is carried out over a wide area. For example, in U.S. Pat. No. 5,199,867 an outwardly divergent fan-shaped fuel jet is sandwiched between two similarly shaped oxidant jets. The lower oxidant jet is designed to produce a low pressure field to influence the fuel jet and thereby spread the combustion out over a wide area. Alternately, as illustrated in U.S. Pat. No. 5,299,929 the fuel jet can be designed to produce a low pressure field to influence the oxidant jets. In the former case the fuel is aspirated into the oxidant and in the latter case, the oxidant is aspirated into the fuel. In another type of oxy-fuel burner or burner system, shown in U.S. Pat. No. 4,927,357 a divergent fan-shaped oxidant jet is located below a burner or fuel jet to produce a low pressure field to attract the fuel jet and thereby position the flame downwardly, towards the melt. The methodology involved is known in the art as oxygen lancing.
Any of the foregoing burners or systems are optimized to operate with a specific type of fuel, either a gaseous or a liquid fuel. Very often though, the cost of the fuel varies in dependence upon the time of the year or sometimes even the time of day in which the fuel is used. The cost of ensuring availability of gaseous fuels during periods of peak demand ("non-interruptable rates") can be sufficiently significant that it becomes cost effective to shut down the furnace and replace the fuel nozzle used for the gaseous fuel with a fuel nozzle that is for a liquid fuel. As can be appreciated, though perhaps cost effective, the shut-down is an expensive production delay.
As will be discussed the present invention provides an oxy-fuel burner system that is designed to accommodate either liquid or gaseous fuel or both with a very rapid turnaround time when switching between the fuels.